Deck Operations
1. Mooring and Anchoring Procedures 1 Responsibility
1.11 Anchoring Equipment and Anchoring .1 Basic Principles
1.10.2 Foc’s’le Watchkeeping Arrangements
Although tending of moorings is not required, an experienced crew member should be posted forward at all times to observe the moorings and advise if the vessel starts to ride up to the buoy or starts to yaw excessively.
The crew member must communicate with the Officer on Watch by radio at least every 15 minutes.
1.10.3 Equipment to be Available
When mooring to a SBM, essential equipment such as a large axe, sledgehammer and a crow bar should be readily available.
1.11 Anchoring Equipment and Anchoring 1.11.1 Basic Principles
Anchors are used for three basic reasons:
• To anchor the vessel in one place for a period of time;
• To assist in a controlled manoeuvre in a restricted area;
• To act as a brake in an unplanned emergency manoeuvre.
It must be noted that anchors are only designed to hold the ship at anchor in moderate weather conditions.
Factors which can affect anchor holding capacity include:
• The nature of the bottom;
• The amount of cable laid out;
• The wind force;
• The rate of the tide;
• Significant waves or swell;
• Manoeuvring with an anchor down, and the forces applied to it whilst using the engines.
The greater each of the above forces is, the more likely it is that the anchor will drag, and obviously a combination of any of the above factors will act to reduce the ability to hold. In a worst case scenario excessive forces may lead to the loss of the anchor.
1.11.2 Anchoring Equipment 1.11.2.1 Windlass
The most important part of the windlass is the brake. The brake lining must be regularly inspected for wear. It should be borne in mind that the lining is secured to the brake band by bolts, the heads of which are pan-shaped and which protrude into the brake lining. Excessive wear of the lining will mean that the heads of the bolts will be rubbing against the brake drum which will result in damage.
Some vessels are fitted with brakes which, in addition to the brake tensioning screw, also have a bottle screw type brake adjustment. Unless this bottle screw is correctly adjusted, it is possible that the crosshead holding the brake tensioning screw will contact the winch foundation and prevent the brake being fully tightened. There should be at least 30 mm of clearance between the bottom of the cross head and the winch foundation. The most effective way to check that a brake is being fully applied is to tighten it and then, with the windlass in gear, attempt to move the gypsy.
The Master must know the amount of cable that the windlass is capable of lifting and the weight of each shackle of cable. A safety factor of at least 10% of that weight must be allowed
when anchoring in deeper water and allowance must also be made for the reduced efficiency of the windlass as it ages. The information must be readily available on the bridge.
1.11.2.2 Chain Clearing Bars
The windlass gypsy is provided with anchor cable clearing bars. The purpose of these bars is to prevent the cable jamming in the gypsy and returning around it.
It is important that these bars are in place. If for any reason they become dislodged or damaged, they should be repaired at the earliest opportunity.
1.11.2.3 Anchors
The holding power of an anchor is mainly a function of the fluke area, and for an ordinary stockless anchor it is about three times its weight. However, as vessels have increased in size, the weight of anchors has increased but not proportionally, and the holding power of such anchors on ships the size of a VLCC has thus become marginal.
1.11.2.4 Anchor Cable
The anchor cable is fitted in shackles or shots, each of 90 feet or 27.5 metres in length.
Kenter shackles are used to join the shackles.
Each shackle should be marked to allow easy identification of how much cable has been laid whilst anchoring. The most effective way of doing this is to paint the number of links corresponding to the number of shackles either side of the joining shackle in white paint.
However, this is not particularly easy to do, and the paint rarely lasts very long. An equally useful method, although less visually effective, is to mark the stud of the link corresponding to the number of shackles with Tespa band.
Kenter shackles must be checked for condition whenever the anchor is heaved up. The parts of a Kenter shackle are secured together with a tapered spile pin. The pin itself is held in place by a lead plug and the Officer in charge on the foc’s’le should check that the plug and spile pin are in place whilst the anchor is being heaved in.
1.11.2.5 Anchor Cable Bitter End
The inboard end of the cable, the bitter end, is attached to the chain locker bulkhead by a device which allows the cable to be released from outside the chain locker. This connection must be regularly maintained to ensure that in case of an emergency it is free. It is likely that a sledge hammer will be required to release the cable and such a hammer must be dedicated for this purpose and must be stored adjacent to the release point.
Maintenance must also be carried out to maintain the watertight integrity of the connection.
Where a pin or other device passes through a gland, this must be watertight. Pins are generally fitted with an ‘O’ ring, and this should be regularly checked and greased.
1.11.2.6 Bow Stopper
The primary function of the bow stopper is to take the weight when the vessel is at anchor.
There are three general types of devices which secure the cable against movement:
• A guillotine bar
• A pawl
• A screw clamp
Immediately the vessel is brought up, the bow stopper should be closed and secured using the locking pin. The anchor cable should then be walked back just enough to locate the cable securely against the stopper and to take the weight off the windlass brake, and the windlass
must be taken out of gear. It is important, in order to prevent damage to the windlass and its bearings that the weight is not taken solely on the windlass brake.
A secondary device for securing the cable at sea should be provided on the forward end of the stopper, usually consisting of a turnbuckle and a wire strop. The strop is passed through the cable at the top of the hawse pipe. Under no circumstances must chain be used. Chain is too inflexible, and in heavy seas with the bow panting, there is risk that damage to, or loss of, the anchor may occur.
Bow stoppers are either fitted with rollers or guides to facilitate the deployment of the cable through the change of angle between the head of the gypsy and the hawse pipe. Where rollers are fitted, these occasionally develop cracks, which can result in large pieces of metal becoming detached during operation. They must therefore be regularly checked to ensure they remain intact.
1.11.2.7 Spurling Pipes
The spurling pipe is the point below the gypsy where the anchor cable enters the chain locker.
It should be provided with arrangements to secure it against the entry of water.
Normally this will consist of two steel plates placed one each side of the cable, and which are either sealed with cement or other such suitable material, and then covered with canvas or sheeting.
When proceeding on voyage where there is any possibility of shipping water over the foc’s’le, the spurling pipes must be adequately and securely sealed well before entering such conditions.
1.11.2.8 Hawse Pipes
Hawse pipes should either be protected by railings or have steel covers fitted, in order to prevent personnel accidentally stepping into the opening.
Cable washers should be maintained in good order and must be used to clean the cable whenever necessary. Significant amounts of mud must not be allowed to pass into the chain locker, as this will lead to the blockage of the suction and subsequent corrosion.
1.11.3 Anchoring Procedures 1.11.3.1 Nature of the Bottom
The nature of the bottom has more influence on the holding power of anchors than any other single factor:
• Mud - high coefficient of friction, good holding power, flukes normally penetrate easily;
• Sand - half the holding power of mud, reasonably good, allows the anchor to penetrate completely and cover the flukes;
• Rock - very poor holding ground. The holding power is generally about one third of the weight of the anchor. On a hard bed such as rock, the anchor drags and will slide along until it comes to a soft patch. The danger here is that the anchor may lie on the fluke points and if during dragging it comes up against an obstruction, then damage may result.
1.11.3.2 Amount of Cable to Use
As a general rule, the scope (the amount of cable outside the hawse pipe) to be veered should be about five to seven times the depth. Therefore for a 35 metre depth the amount of cable to use should be about 200 metres, or 7 shackles of cable.
In practice other factors will need to be taken into consideration such as the quality of the holding ground, the wind, current, and length of stay. In crowded anchorages, it may not be possible to use the optimum amount of cable.
The cable should lie on the seabed for some distance between the anchor and where the catenary begins. If the cable is off the bottom and the angle between it and the anchor shank is 5 degrees, the tendency is to lift the anchor out of the bottom and the holding power can be reduced by as much as 25%. If this angle becomes 15 degrees the loss of holding power can increase to 50%.
If the anchor drags, weather permitting the normal practice is to veer more cable until the anchor holds. This ensures that the cable is lying on the seabed, as well as providing additional resistance.
1.11.3.3 Anchoring
Anchoring is a delicate procedure and should never be rushed. It is also a practical operation for which practical training is necessary but rarely given. Masters should take every opportunity to offer such training to junior Officers.
The clearing of anchors may be carried out by qualified rating, but the walking out of the anchor prior to letting go must be supervised by an officer. He must check that the brake is fully tightened before removing the compressor bar or guillotine. The anchoring operation itself must also be supervised by a qualified deck officer. Prior to anchoring, the Master must select a suitable position, clear of underwater obstructions, pipelines and cables, offering good holding ground, and one which provides a suitable swing circle clear of other vessels.
Whilst at anchor, a continuous watch must be maintained, not only to ensure that the vessel remains in position, but also to look out for other traffic.
Prior to anchoring, a meeting should take place between the Master and the Officer supervising the anchoring so that the procedure can be discussed. The Master must make his intentions and requirements clear to the Officer.
The anchor to be used must be decided, and the decision should take into account any anticipated changes to the weather conditions or tide which may result in a change in heading.
Consideration must always be given to the fact that a second anchor may have to be let go.
It is important that the Officer understands that once the anchor has been let go the Master must be continuously updated as to the amount of cable paid out, the direction it is leading, the weight, and the movement of the vessel in relation to the cable. He should be prepared to act decisively and quickly in advising the Master as to what action to take should it appear likely that excessive weight might come on the cable.
The anchor should be let go with the heading the same as that anticipated when brought up – head to tide and wind. When approaching an anchorage, the direction other vessels are lying in will indicate how the approach should be carried out. Every effort must be made to avoid changes of course immediately prior to letting go the anchor. The vessel should be making a small amount of sternway when the anchor is let go to avoid a foul hawse.
The depth of water will determine how the anchor is to be let go. In depths of less than 25 metres, the anchor can be walked back to just above the water and then let go on the brake.
However, in deeper water and on large vessels with heavy anchors, it should be walked back to a few metres above the seabed and then let go on the brake. Provided the Master is
confident that the vessel can be satisfactorily controlled, the anchor and cable may be walked out entirely, which method allows the most control.
On larger vessels a small amount of movement can generate significant forces on the anchor and cable and anchoring such vessels takes time and care. The slightest movement of a large ship will have a huge momentum which the windlass brake will be unable to hold.
As the cable runs out, the brake should be carefully applied to control the rate. The cable must not be allowed to run freely out at high speed.
Provided the deck Officer keeps the Master fully informed about the direction of the cable and the weight on it, the latter can use the engines either to reduce the weight on the cable, or put more weight on it to avoid it piling up on the bottom.
Once the required amount of cable has been paid out, the windlass brake should be tightened and the cable observed to see the weight come on and then off with the anchor holding. At that point the vessel can be considered to be ‘brought up’, and the fact reported to the bridge.
If the anchor is dragging, it should be observable through the motion of the cable.
Personal protective equipment must be used by all persons involved in anchoring on the foc’s’le. The amount of debris which can exit from the spurling pipe at high velocity can be significant.
Some vessels are fitted with equipment which allows the anchor to be let go from the bridge.
This function is designed to be used only in an emergency and should not be used during normal anchoring operations.
1.11.3.4 Recovering the Anchor
The effect of deteriorating weather and heavy seas can cause significant problems both in the risk of the loss of the anchor and in the safety of the personnel who have to go forward to heave up. The decision to heave the anchor must be made in good time.
The heaving of an anchor under normal conditions again relies upon the communication between the Officer forward and the bridge.
Once the anchor is aweigh the fact should be reported to the bridge. The anchor should be sighted as quickly as possible to confirm that is free of significant quantities of mud, or of debris, cables, ropes etc., and the fact reported to the bridge. If necessary the anchor can be cleaned by leaving it under the water for a period.
The period between the anchor breaking the surface and coming to the hawse pipe is critical, particularly if the vessel is rolling, and care must be taken to prevent a swinging anchor coming heavily in contact with the hull.
1.11.3.5 Emergency Anchoring
There are several types of emergency when anchors will be used:
• Loss of steering in shallow waters where collision or grounding is imminent;
• Loss of power and danger of drifting on to a lee shore;
• An inability to stop the vessel in case of either engine failure or excessive speed.
In either case the control of the vessel will not be absolute, and there will be a risk that a significant amount of weight might be put on the cable. The experience of the personnel on the foc’s’le will be invaluable in such a situation, and the way the anchor is allowed to run out must be very carefully managed and controlled on the windlass brake.
If time allows, the anchors can be walked out until they are just on the bottom. The risks in carrying out such a manoeuvre whilst travelling at speed are obvious, but the anchors will have a braking effect.
Every situation will be assessed based on the state of the emergency, the size of the vessel and its momentum, and damage limitation. The loss of an anchor and windlass is preferable to the grounding of the vessel.
1.11.3.6 Manoeuvring Whilst at Anchor
It is occasionally necessary to make a lee for small craft to come alongside whilst at anchor.
The fact that the climatic conditions are such that it is necessary to make a lee will generally mean that the only course of action is to heave up the anchor, manoeuvre to allow the transfer process to take place, and then re-anchor afterwards.
In heavy seas, wind, or tide, the strain placed on the cable and stopper becomes unacceptable if the engines are used to put the vessel beam on, or nearly beam on to the weather. With the bow stopper in use, there is no ‘give’ in the system and failure of a component will be likely.
Masters should only consider making a lee whilst at anchor in relatively calm conditions in accordance with good seamanship.